1. Field of the Invention
The present invention relates to vises and more particularly to a vise attachment having a series of independently positioned blades or elements for automatically conforming to the surface contours of irregularly-shaped objects. The invention further relates to a cost efficient, low complexity vise attachment for automaticaly accommodating objects having irregular contours in multiple axis and which resets itself for receiving new objects upon removal of a previously held object.
2. Background
There has long been a need in many endeavors, including advanced technology machining, aerospace development, and scientific research, to hold or clamp irregularly-shaped objects in a fixed position for machining, inspection, or assembly work. However, many of the irregularly-shaped objects have highly complex and convoluted surface angles, structures, or contours which make holding such objects very difficult. In the past, a number of clamps might be used in combination with various shims, filler blocks, or specialized jigs to hold such objects. It is not uncommon in the aerospace industry, for example, to manufacture highly specialized brackets or jigs for holding key parts or components during certain assembly or machining operations. However, this is both time consuming and costly in terms of the extra materials and parts consumed.
Therefore, a variety of specialized holding and clamping devices have been developed in an attempt to accommodate irregularly-shaped objects. Examples of such devices are found in U.S. Pat. Nos. 3,818,646, 4,047,709, and 2,658,415. While these and other devices represent an improvement in the art of holding irregularly-shaped objects, they suffer from several drawbacks that have prevented widespread application in the machining arts.
U.S. Pat. No. 3,818,646 illustrates a special fixture for holding precisely shaped parts. The fixture employs a series of opposing fingers to press against opposite sides of a curved or irregularly-shaped object and hold it in place. One or more set screws and bolts are then pressed laterally against the sides of the fingers to fix them in position against the object. This type of fixture finds use in holding a curved turbine blade or similar object for final assembly or machining.
Apparatus exemplified by U.S. Pat. No. 3,818,646 are similar to the aforedescribed jigs and specialty fixtures developed in the art for holding irregularly-shaped parts. This type of fixture is a stand alone device usable only with a limited range of parts or objects for which it has been specifically dimensioned. The fixture has a preplanned and fixed maximum separation distance between opposing fingers that limits the thickness of objects for which this apparatus is usable. Also, the fingers require manual manipulation by an operator in order to conform to a new object or for releasing a previously held object. In addition, the pressure applied laterally to the sides of the fingers to lock them in place is insufficient to prevent finger movement under many clamping loads.
U.S. Pat. No. 4,047,709 discloses a clamping device that uses a clamping jaw having a plurality of movable plungers extending from one face of a housing. The plungers interact with the exterior surfaces of an irregularly-shaped object to position themselves at various projected lengths from the face of the clamping device. Hydraulic pressure is then used to press a medium, generally comprising spherical balls, into a series of annular depressions on the sides of the plungers to lock them in place.
Apparatus exemplified by U.S. Pat. No. 4,047,709 require a source of hydraulic fluid and some form of pressure control apparatus for operation. This increases complexity, cost, and maintenance, as well as sources of device failure. Unlike the U.S. Pat. No. 2,658,415 device, the plungers can return to a "neutral" position after an object is removed and pressure is applied to the medium. However, the apparatus required for operation and overall structure generally preclude utilization of this type of clamping device in applications other than on specially configured work surfaces or assemblies. Also, there are limitations on using pressure actuation on very thin or fragile parts.
U.S. Pat. No. 2,658,415 discloses an adjustable vise assembly for holding irregularly-shaped objects. The vise utilizes a pair of opposing jaws, each having a series of individual jaw segments that are extendable at different lengths from the face of the jaw. A reservoir of displaceable material positioned behind the segments distributes the load to adjacent segments and a back housing wall. Various cams and levers are used to press against the jaw segments in order to lock them in place or move them to new positions. A variety of parts may be repetitively inserted in the jaws of this vise assembly because the jaws retain a given configuration.
Devices exemplified by U.S. Pat. No. 2,658,415 are very large and bulky devices suitable only for use in connection with large scale milling machines and the like. This type of device is a complex and costly stand alone vise assembly intended to replace existing equipment a user may already have for holding objects. While such devices clamp irregular surfaces for repetitive operations, they do not automatically realign themselves to a "neutral" position for accepting new irregularly-shaped objects. That is, manual adjustment or actuation of the jaw elements is required by an operator to return the clamping device to a non-aligned state for accommodating a new object.
What is needed then is a clamping device that is usable in a variety of clamping and machining situations, especially as related to existing vise assemblies, and automatically adjusts itself between a holding configuration and a neutral position upon removal of an irregularly-shaped object. It is very desirable to have an apparatus that is usable with existing vises or holding devices as well as having a minimum bulk and external structure. It is desirable to achieve these goals in a device which does not utilize complex pneumatic or media manipulation techniques or apparatus and is simple and reasonably inexpensive to manufacture. It is also desirable that any clamping device be capable of holding very thin or fragile objects as well as bulky or strong objects.